Solder is Pooling on a Foil Project

I just finished foiling a project and am experiencing a problem with laying down the solder. It is not flowing, but rather pooling. Meaning I have to push it to get it to lay on the foil and stretch it instead of beading it. Spool is new 60/40, foil is not old or oxidized, using same temperature on iron as usual. I changed spools, changed irons, and still the pooling and globing. First time in 20+ years this has happened. Glass was clean, no oils or old stuff on it. Any ideas? I am stumped and have done a half dozen pieces in the last month, with all the same stuff, no problems. Just now. Any help would be appreciated.

Answer

Your flux might be contaminated. Try using a new bottle of flux, pour some in a clean container to use while you're soldering, then dispose of the rest. Dipping straight into the bottle will contaminate the flux quickly.

Did you have a fan blowing on you and the glass while you were soldering? That can cause problems with the way the solder flows.

What about the foil? Did you use a new roll of foil? That could very well be the culprit. I have seen areas on foil, even a roll you have been using with success, that just won't let the solder flow, no matter what you do.

One other thing you could do is to check your temp controller (if you use one). It may not be working properly and is keeping your iron too cool.

Those are the only things I can think of. Hopefully, it won't happen again.